This application claims the priority of Korean Patent Application No. 2003-74672, filed on Oct. 24, 2003, in the Korean Intellectual Property Office, the contents of which are incorporated herein in their entirety by reference.
1. Field of the Invention
The present invention, relates to a method of manufacturing a bipolar-complementary metal oxide semiconductor (BiCMOS) into which a bipolar transistor and a CMOS are integrated, and more particularly, to a method of manufacturing a BiCMOS using a heterojunction bipolar transistor (HBT) as a bipolar transistor.
2. Description of the Related Art
With the development of ultrahigh-speed communication technology, a high-frequency transistor has been developed rapidly. Recently, a SiGe HBT is used in a high-frequency transistor device. A SiGe HBT is different from a normal bipolar transistor in that a base is formed of a SiGe epitaxial layer. Since SiGe has a smaller energy band gap than Si, an HBT having a base formed of SiGe has improved current gain and operating speed. In addition, even when a concentration of a dopant in the base is increased, the current gain is not reduced, but base resistance is reduced. As a result, a noise figure of the device can be reduced. Moreover, since operating voltage is decreased, power consumption can be reduced. Meanwhile, a transition frequency (fT) and a maximum oscillation frequency (fMAX) can be increased by adjusting the content and the distribution of Ge in SiGe. Accordingly, a SiGe HBT is widely used as a high-frequency device having fT and fMAX of 50 GHz or higher for a communication device.
Such an HBT is integrated with a CMOS transistor, thereby forming a BiCMOS device. Usually, a BiCMOS has a structure in which a CMOS transistor is integrated with a bipolar transistor on a silicon substrate. In more advanced BiCMOS technology, a SiGe HBT instead of a bipolar transistor is used. A base made of SiGe is used for a high-performance HBT to process an analog signal, and a CMOS transistor is used to process a digital signal and store data.
Since such an SiGe HBT has the same performance as existing III-V compound semiconductors and can be subjected to silicon manufacturing processes, it can be manufactured at a low cost. In addition, since silicon semiconductor technology can be used, a system-on-chip (SOC) can be realized, thereby increasing applicability.
In conventional SiGe BiCMOS manufacturing processes in which existing SiGe HBT manufacturing processes are combined with existing CMOS transistor manufacturing processes, an HBT is formed after a CMOS transistor is formed, or HBT manufacturing processes are inserted in the middle of manufacturing a CMOS transistor. In such conventional methods of simply adding existing HBT manufacturing processes to existing CMOS transistor manufacturing processes, performance of a CMOS transistor may be degraded due to a different type of process added to the CMOS transistor manufacturing processes. For example, when an emitter dopant drive-in process is performed to manufacture an HBT after a source/drain of a CMOS transistor is formed, a profile of a source/drain junction is changed due to a thermal budget, thereby degrading performance of the CMOS transistor.
In addition, to perform photolithography to manufacture an HBT in a conventional method of adding existing HBT manufacturing processes to existing CMOS transistor manufacturing processes, 7 or 8 masks are additionally required. That is, the number of masks and the number of processes used in fabricating the device are increased.